TWI911215B - Storage and delivery of antimony-containing materials to an ion implanter - Google Patents

Abstract

A novel method, composition and storage and delivery container for using antimony-containing dopant materials are provided. The composition is selected with sufficient vapor pressure to flow at a steady, sufficient and sustained flow rate into an arc chamber as part of an ion implant process. The antimony-containing material is represented by a non-carbon containing chemical formula, thereby reducing or eliminating the introduction of carbon-based deposits into the ion chamber. The composition is stored in a storage and delivery vessel under stable conditions, which includes a moisture-free environment that does not contain trace amounts of moisture. The storage and delivery container is specifically designed to allow delivery of high purity, vapor phase antimony-containing dopant material at a steady, sufficient and sustained flow rate.

Description

Storage and delivery of antimony-containing materials to ion implantation machines

This invention relates to a novel storage and transport container for antimony-containing materials used in ion implantation, and to suitable conditions for storing and transporting materials used in ion implantation procedures.

Ion implantation is a key process in semiconductor/microelectronics fabrication. Typically, ion implantation is used in integrated circuit fabrication to introduce dopants into semiconductor wafers. Generally, for semiconductor applications, ion implantation involves introducing ions from a doping gas (often also called a dopant) into the semiconductor wafer to alter the wafer's physical, chemical, and/or electrical characteristics in a desired manner. The desired dopant is introduced in minute quantities into the semiconductor wafer, forming doped regions at a desired depth on the wafer surface. The selected dopant is bonded to the semiconductor wafer to create a charge carrier, thereby altering the semiconductor wafer's conductivity. The concentration or amount of impurities introduced into a wafer determines the conductivity of the doped regions. In this way, several impurity regions are created to form transistor structures, isolation structures, and other electronic structures, which together function to form a semiconductor device.

An ion source is an ion beam used to generate ion species from a source doped gas. The ion source is a key component of an ion implantation system, used to ionize the doped gas to generate the specific doped ions to be implanted during the implantation procedure. The ion source chamber contains a cathode, such as a filament made of tungsten (W) or a tungsten alloy, which is heated to its thermal ionization temperature to generate electrons. These electrons are accelerated toward the arc chamber wall and collide with doped source gas molecules in the arc chamber to generate plasma. The plasma contains dissociated ions, radicals, and neutral atoms and molecules from the doped gas species. The ion species is extracted from the arc chamber and then separated from other ion species based on mass. Only ions in the beam with a specific mass-to-charge ratio can pass through a filter. The selected mass of ions containing the desired ion species is then directed toward the target substrate and implanted into the target substrate at the desired depth and dosage.

Semiconductor device technology currently utilizes specific amounts of various dopants to produce p-type and n-type semiconductors, which are considered building blocks for manufacturing transistors and diodes. The main difference between p-type and n-type dopants lies in the type of charged substance introduced into the semiconductor lattice. P-type dopants are used to create "holes" in semiconductor materials by generating electron vacancies in the valence band, while n-type dopants are used to generate free electrons in semiconductor materials. Antimony (Sb) is an example of a commonly used dopant required for today's electronic devices. Sb, an n-type dopant with many suitable applications, continues to attract interest in the semiconductor industry. For example, indium antimonide (INT) is a narrow bandgap III-V semiconductor used in infrared detectors. INT is also used to form ultra-shallow p-n junctions in finfield field-emitting transistor (FFET) devices, threshold voltage regulation of channels in metal-oxide-semiconductor field-emitting transistors (MOSFETs), breakdown-stop halogen implantation in p-type metal-oxide-semiconductor (MOS) devices, and source-drain regions in germanium-n MOSFETs.

Currently, solid-state sources of Sb are used as dopant materials. Elemental Sb metal can be used for ion implantation by placing it close to a filament. During ion implantation, the filament is heated sufficiently to cause Sb to evaporate and collide with electrons to generate Sb-containing ions for doping. However, this method can cause Sb to deposit on the chamber walls or the filament, shortening the filament's lifespan. Solid-state compounds of _Sb are also used as dopant sources, such as _SbF₃ , _SbCl₃ , and _Sb₂O₃ , but these compounds must be heated to above 160°C to generate the sufficient vapor volume required for ion implantation. In addition, all flow lines in the system are typically heated to prevent the Sb solid source from recondensing before reaching the arc chamber.

Given the operational challenges of implanting Sb-containing ions with a given solid Sb source, gaseous Sb sources have been considered. In particular, _SbH3 and _SbD3 have been proposed as gaseous Sb sources, but these compounds are unstable and decompose at room temperature.

For these reasons, there is currently an unmet need for suitable storage and delivery containers for antimony-doped compositions intended for ion implantation, allowing for controlled delivery.

This invention may include any of the following embodiments in various combinations, and may also include any other embodiments described in the following specification and accompanying drawings.

This invention relates to a storage and transport system using antimony-doped compositions. The storage and transport system disclosed herein has been found to improve the ease of delivery to ion implantation procedures and substantially reduce the accumulation of Sb-containing deposits in the ion chamber.

In the first scenario, a storage and transport container operating at sub-atmospheric pressure is configured to transport a high-purity vapor-phase antimony-containing material. The container comprises a storage and transport vessel configured to store the antimony-containing material in a liquid phase under sub-atmospheric pressure conditions, whereby the liquid phase is substantially in equilibrium with the high-purity vapor-phase antimony-containing material, and the high-purity vapor-phase antimony-containing material is subjected to evaporation at sub-atmospheric pressure. The high-purity gas phase has a total volume of approximately 95% or greater; the storage and transport container comprises multiple walls with sufficient surface area to contact the liquid phase, and further wherein these walls exhibit thermal conductivity to enhance heat conduction to the liquid; the storage and transport container is characterized by the absence of external heating and carrier gas during the delivery of the high-purity gas-phase antimony-containing material.

In the second embodiment, a storage and transport container operating at sub-atmospheric pressure is configured to transport a high-purity vapor-phase antimony-containing material. The container comprises a storage and transport vessel configured to store the antimony-containing material in a liquid phase under sub-atmospheric pressure conditions, whereby the liquid phase is substantially in equilibrium with a predetermined volume of high-purity vapor-phase antimony-containing material occupying a headspace within the storage and transport vessel. A high-purity vapor-phase antimony material is subjected to a vapor pressure less than atmospheric pressure. The high-purity vapor phase, based on a predetermined volume of the headspace, is approximately 95% by volume or greater. The dimensions of the predetermined volume of the headspace are adjusted to receive a sufficient quantity of the high-purity vapor-phase antimony material. The storage and transport container is characterized by the absence of external heating and carrier gas during the delivery of the high-purity vapor-phase antimony material.

In the third state, a high-purity antimony-containing material in a storage container comprises a liquid phase and a gas phase, wherein the gas phase contains a total amount of gaseous impurities ranging from 0 to 5 volume %, wherein the gaseous impurities comprise 0 to 4 volume % N ₂ , 0 to 0.5 volume % O ₂ , 0 to 0.49 volume % HF, 0 to 0.01 volume % H ₂ O, and the remainder is the antimony-containing material in the gaseous phase.

In the fourth state, a high-purity antimony-containing material in a storage container comprises a liquid phase and a gas phase. The liquid phase contains a total amount of liquid impurities ranging from 0 to 1 volume % of impurities, wherein the liquid impurities include 0 to 0.1 volume % of _N2 , 0 to 0.1 volume % of _O2 , 0 to 0.6 volume % of HF, 0 to 0.1 volume % of _SbF3 , 0 to 0.1 volume % of _Sb2O3 , _and the remainder is the antimony-containing material in the liquid phase.

In the fifth aspect, a method for preparing a storage and transport container at sub-atmospheric pressure, the container being configured to transport a stable, continuous, and sufficiently flowing high-purity vapor-phase antimony source material, the method comprising the following steps: providing a container having multiple walls with a thermal conductivity of 5 W/m*K; passivating the multiple walls with fluorine; then introducing a liquid antimony-containing material into the container in the presence of an inert gas; generating a predetermined headspace volume greater than or equal to about 1 L, the predetermined headspace volume containing trace impurities; and evaporating a sufficient amount of the antimony-containing material. The process involves: forming a gaseous phase within a predetermined headspace volume, wherein the evaporation step is performed without external heating; freezing the antimony-containing material in the liquid phase to form a frozen antimony-containing material; condensing the antimony-containing material in the gaseous phase from the predetermined headspace volume to form a condensed high-purity gaseous phase; venting nitrogen, water vapor, inert gases, and any other gaseous impurities from the predetermined headspace volume; allowing the temperature of the condensed gaseous phase to increase in order to form a high-purity gaseous phase within the predetermined headspace volume; and allowing the temperature of the frozen antimony-containing material to increase in order to reform into a liquid phase.

In the sixth aspect, a method for using a storage and delivery container filled with high-purity antimony-containing material at sub-atmospheric pressure includes: operatively connecting the container to a downstream ion implantation tool; establishing a pressure downstream of the sub-atmospheric pressure storage and delivery container at a pressure less than the vapor pressure of the high-purity vapor antimony-containing material occupying a predetermined headspace volume of the container; actuating a valve to an open position; and dispensing from the predetermined headspace volume of the container without heating. An antimony-containing material, delivered as a high-purity gaseous phase at a flow rate of 0.1 sccm or greater without a carrier gas; the high-purity gaseous antimony-containing material flowing toward an ion implantation tool at a flow rate of 0.1 sccm or greater without a carrier gas; and the evaporation of additional antimony-containing material from the corresponding liquid phase in the container without heating, while continuing to supply high-purity gaseous antimony-containing material from the headspace at a flow rate of 0.1 sccm or greater.

100: Gas Box

101: Sb-containing liquid source material

102: Flow control device

103: Arc Chamber

104: Ion Beam Extraction (System)

105: Quality Analyzer/Filter

106: Acceleration/Deceleration

107: Terminal station, embedded terminal station

108: Target workpiece

200: Gas Box

201: Sb-containing liquid source materials

202: Flow control device

203: Plasma Chamber

204: Target workpiece

205: Platform

300: Storage and transport containers

310: Port of Entry

311: Valve

320: Export Port

321: Valve

330: Vacuum-actuated check valve

335: Headroom

336: Headroom

401: Headroom

The purpose and advantages of the present invention will be better understood from the following detailed description of preferred embodiments with reference to the accompanying drawings, wherein the same numbers throughout denote the same features, and wherein: [Figure 1] shows a wire-based ion implantation system incorporated into the principles of the present invention; [Figure 2] shows a plasma-immersed ion implantation system incorporated into the principles of the present invention; [Figure 3] shows an exemplary storage and transport container incorporated into the principles of the present invention; and [Figure 4] shows an alternative storage and transport container incorporated into the principles of the present invention.

The relationship and function of the various elements of the present invention are best understood from the following detailed description. Within the scope of this disclosure, various arrangements and combinations of features, forms, and specific embodiments are described in detail. This disclosure may therefore be specified as including, constituting, or substantially constituting any such combination and arrangement of, including, or consisting of, one or more of these specific features, forms, and specific embodiments or alternatives thereof.

This invention may include various combinations of any of the following embodiments, and may also include any other embodiments described in the following description or accompanying drawings. As used herein, the term "embodiment" means a specific embodiment that is illustrated by way of example but is not limited thereto.

As used herein and throughout, the terms “Sb-containing ion” or “Sb ion” mean a variety of Sb ion species suitable for implantation into a substrate, including Sb ions or Sb-containing ions (e.g., Sb ⁺ or Sb2 ⁺ ) and oligomeric ions (e.g., but not limited to _Sb2 ⁺ ).

As used herein and throughout, "substrate" refers to any material to which ion implantation is required, including but not limited to wafers or other sliced or unsliced materials or similar targets, formed of any suitable material, including silicon, silicon dioxide, germanium, gallium arsenide, and their alloys, with other materials such as those doped with ions implanted therein.

It should be understood that "Sb" and "antimony" will be used interchangeably herein and throughout the text, and are intended to have the same meaning. Reference to "Sb-containing material," "Sb-containing source material," or "Sb source material" is intended to refer to the liquid-phase antimony material of the present invention and the corresponding gas phase in substantial equilibrium with the liquid phase. "Sb-containing liquid source material" is intended to mean the material of the present invention in substantial equilibrium with the corresponding gas phase.

As used herein and throughout, the term "vessel" (or "container") may be used interchangeably and is intended to mean any type of container suitable for the storage, filling, transport, and/or conveying of materials, including but not limited to cylinders, dewars, bottles, troughs, barrels, bulks, and microbulks. Consistent with this usage, the terms "storage and delivery vessel" and "storage and delivery container" will be used interchangeably herein and throughout the text, and are intended to refer to a container specifically designed for storing a source of antimony-containing material in a manner that allows additional liquid antimony-containing material within the container to evaporate into a predetermined headspace volume at a delivery rate equal to or greater than the gaseous flow rate of the delivery.

As used herein and throughout, “reduce” (reduced or reduction) refers to ion implantation procedures and is intended to mean: (i) shortening, inhibiting, and/or delaying the onset or occurrence of harmful events (e.g., reducing decomposition reactions, reducing ion short circuits); or (ii) reducing the quantity to an unacceptable level to achieve the intended purpose (e.g., reducing flow to the point of unsustainable plasma); or (iii) reducing the quantity to a non-substantial level without negatively impacting the intended purpose (e.g., reducing the amount of oligomers without compromising flow stability into the arc chamber); or (iv) a significant reduction compared to conventional practice, but without altering the desired function (e.g., reducing heat in the tube). [Tracing] However, it maintains the material's gaseous phase, preventing it from re-condensing along the pipe.

As used herein and throughout the text, "about" or "approximately," when referring to measurable values (such as quantities or amounts of time), means to cover variations of ±20%, ±10%, ±5%, ±1%, or ±0.1% from the specified value, as such variations are appropriate.

As used here and throughout the text, "high purity" means 95% by volume or greater.

As used herein and throughout, "ambient condition" refers to environmental conditions, including ambient temperature and ambient pressure, that are in direct contact with the storage and transport container filled with the Sb-containing material of this invention.

As used herein and throughout, "trace amount" means that the concentration of impurities (preferably including water vapor, nitrogen, and any other gaseous impurities) in the aggregate is 5% by volume or less.

This disclosure can be presented in a range format to represent the various aspects of the invention. It should be understood that the range format is for simplicity only and should not be considered a limitation on the scope of the invention. Accordingly, a range description should be considered as specifically disclosing all possible subranges and individual numerical values within that range. For example, a range description from 1 to 6 should be considered as specifically disclosing subranges (e.g., from 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 6, 3 to 6, etc.) and individual numbers within that range (e.g., 1, 2, 2.7, 3, 4, 5, 5.3, 6, and any complete and partial increments therebetween). This applies regardless of the range width.

The use of antimony-containing materials for ion implantation has been recognized. In this regard, Kasley et al. disclosed the use of _SbF5 as the antimony source, which involves heating an _SbF5 container to 52°C to generate sufficient vapor pressure of _SbF5 within the container for antimony implantation into a silicon substrate. While Kasley et al. demonstrated that this approach is feasible for small-scale laboratory settings, this invention recognizes its shortcomings when attempting to scale up for operational applications. Specifically, in operational settings, the _SbF5 vapor generated by heating at higher temperatures (e.g., temperatures above ambient temperature) tends to condense downstream along a flow path extending between the antimony container and the ion implantation tool, as the flow path typically remains within ambient conditions. _SbF5 vapor condenses along the flow path before entering the ion implanter, thus failing to achieve stable, sufficient, and continuous gas phase flow of _SbF5 .

To overcome this deficiency, the present invention recognizes that the user must maintain the entire flow path between the antimony source container and the ion implantation tool at high temperatures. However, from an operational perspective, the system design and operation become more complex for ion implantation systems that require heating equipment to maintain significantly high potentials (e.g., 10kV~100kV). This high potential level can pose safety risks, and the presence of toxic, corrosive, and/or flammable materials in the flow path adjacent to the ion implantation system and heating equipment also poses risks.

The present invention addresses the lack of suitable storage and transport systems for Sb source materials used in ion implantation. Recognizing and considering the aforementioned limitations, the present invention provides a unique solution for storing and transporting antimony-containing materials for ion implantation applications and other applications requiring controlled and continuous flow of gaseous Sb-containing materials to downstream processes.

This invention relates to a container for storing and transporting antimony-containing materials suitable for ion implantation as n-type dopant. The container possesses the following properties: (i) the antimony-containing material can be stored in a liquid phase under ambient conditions at a pressure below atmospheric pressure, wherein the storage conditions are in an impurity-free environment, characterized by the absence of trace amounts of water vapor, nitrogen, and any other gaseous impurities in the headspace of the container, defined herein as having a headspace volume not exceeding approximately 5 volumes. (ii) the antimony-containing material is represented by a carbon-free chemical formula; (iii) the storage and delivery container has a predetermined headspace volume containing gaseous antimony-containing material in substantial equilibrium with the liquid phase, wherein the predetermined headspace volume has a volume greater than 1 L; and (iv) the walls of the storage and delivery container are made of a material with a thermal conductivity greater than 5 W/m-K under ambient conditions; and (v) the storage and delivery system is maintained under ambient conditions during its use in antimony implantation procedures. The storage and delivery container at subatmospheric pressure can provide a continuous and adequately flowing gaseous antimony source material with a purity of 95% by volume or greater and at a continuous, adequate, and stable flow rate, as described herein. More preferably, the purity of the vapor-phase antimony source material is 99% or greater. The storage and transport containers are configured to operate such that the evaporation rate of the liquid-phase antimony-containing material can form a corresponding vapor phase within a predetermined headspace volume without external heating, and this evaporation rate is equal to or greater than the rate at which the corresponding vapor phase is extracted from the predetermined headspace volume during delivery.

The Sb-containing source material has a liquid phase in substantial equilibrium with the corresponding gas phase under storage conditions. The material remains stable at ambient temperature and does not tend to decompose during ion implantation. The liquid Sb-containing material has an appropriate vapor pressure, defined herein as a vapor flow rate that can sustainably supply the arc chamber at a rate of approximately 0.1–100 sccm, preferably 0.3–10 sccm, more preferably 1–10 sccm, and most preferably 1–5 sccm. In particular, the flow rate of the gaseous Sb-containing material is appropriate to generate and maintain a stable plasma during operation of the ion implanter. A stable plasma allows Sb ion implantation to occur at an arc voltage of approximately 50–150 V and a extraction voltage of approximately 1–300 kV across the extraction electrode, thereby generating an Sb ion beam. The Sb ion beam current ranges from approximately 10 μA to 100 mA, resulting in an Sb ion dose of approximately 1 x ^10¹¹ to ¹ x 10¹⁶ atom/ ^cm² entering the substrate.

In one embodiment, the Sb-containing source material of this invention is stored in a container where the liquid and gas phases are in substantial equilibrium, thereby allowing the gas phase to be extracted from the container at ambient temperature without external heating. The applicant has discovered that external heating applied to the container can cause problems. In particular, if external heating is applied to the container but not to the piping, valves, and/or mass flow controllers, the Sb-containing material can condense on the piping, valves, and/or mass flow controllers at temperatures lower than the container. This condensation can cause flow instability and blockage of system components, ultimately preventing the flow of the Sb-containing material. If external heating is applied to the container, the applicant has found that heating must be applied to all components exposed to the Sb-containing material, including piping, valves, and mass flow controllers, such that the temperature of the piping, valves, and mass flow controllers is greater than or equal to the temperature of the container. However, this increases the complexity of the system design, especially in ion implantation systems, because the heating equipment must be maintained at significantly high potentials (10kV~100kV), posing safety risks. For this reason, the Sb-containing material should be able to maintain a stable and sufficient flow rate at ambient temperature without the use of external heating. In one example, the ambient temperature range can be from 10°C to 35°C. The sustainable, sufficient, and stable flow range at ambient temperature is 0.1~100 sccm, preferably 0.3~10 sccm, more preferably 1~10 sccm, and most preferably 1~5 sccm.

In another embodiment of the invention, the Sb-containing source material is stored in a container in a liquid phase in substantial equilibrium with its gaseous phase. This gaseous phase occupies the headspace of the container, which has a predetermined volume into which a sufficient amount of the liquid antimony-containing material can evaporate to form the corresponding gaseous phase. The gaseous Sb-containing source material can be extracted with high purity from the vapor space of the container and transported along a conduit to the arc chamber of the ion implanter under ambient temperature conditions. Advantageously, the vapor headspace provided by the storage container has a predetermined volume greater than 1 L. The inner wall of the storage container has a thermal conductivity greater than 5 W/m-K under ambient conditions and is appropriately in contact with the liquid. In this manner, a sufficient amount of Sb-containing source material evaporates into a gaseous phase at the ambient temperature and flows into the arc chamber at a continuous flow rate of approximately 0.1–100 sccm, preferably 0.3–10 sccm, more preferably 1–10 sccm, and most preferably 1–5 sccm.

The applicant has discovered that the evaporation rate of the liquid Sb-containing source material must be maintained to generate a gaseous flow rate of at least about 0.1 sccm or greater into the arc chamber via conduit. When the evaporation rate of the Sb-containing liquid is at or below a certain threshold, resulting in a gaseous flow rate of the Sb-containing source material of at or below about 0.1 sccm, the gaseous Sb-containing material may flow into the arc chamber via conduit at a rate faster than the evaporation rate of the Sb-containing source material contained in the container. The flow into the arc chamber may be unsustainable and eventually decrease to an unacceptably low level or tend to become unstable. Ultimately, in the worst-case scenario, the flow may stop completely or decrease to the point that the ion beam becomes unstable and malfunctions, necessitating the termination of the entire implantation procedure.

In an alternative specific embodiment, as a feasible means to accelerate the evaporation rate, the liquid source containing Sb may be stored in a storage and transport container maintained at a pressure below atmospheric pressure so that the liquid source material can evaporate at a relatively high rate, which is sufficient to form the required amount of gaseous source material to generate the required flow rate of about 0.1 to 100 sccm, preferably 0.3 to 10 sccm, more preferably 1 to 10 sccm, and most preferably 1 to 5 sccm to the arc chamber. Accordingly, the Sb-containing material from the liquid source evaporates into a gaseous phase at a sufficient rate to replenish the vapor in the head space of the storage and transport container and along the pipes extending to the arc chamber, thereby generating and maintaining a gaseous flow rate of the Sb-containing source material at approximately 0.1–100 sccm, preferably 0.3–10 sccm, more preferably 1–10 sccm, and most preferably 1–5 sccm during the Sb ion implantation operation in the ion implanter.

To provide the necessary storage conditions for evaporation, the storage and transport container is constructed with sufficient headspace volume to retain a sufficient volume of Sb-containing source vapor, allowing the necessary gas phase flow into the conduit extending into the arc chamber. The applicant has found that the storage and transport container is manufactured and constructed with a predetermined headspace volume of ≥0.5L, preferably ≥1L, more preferably ≥1.5L, and most preferably ≥1.8L. Incidentally, it is preferable that the Sb-containing liquid has sufficient surface area exposed to the gas phase within the storage and transport container, and that the liquid has sufficient contact area with the inner wall, to allow the necessary evaporation as the corresponding Sb-containing material in the gas phase flows along the conduit to fill the headspace of the storage and transport container, thereby generating a substantial, stable, and continuous flow of Sb-containing vapor with high purity into the arc chamber. Specifically, combining the liquid contact area as described herein, the surface area of the liquid exposed to the gas phase is preferably at least about 16 ^cm² , more preferably greater than or equal to about 50 ^cm² , and most preferably greater than about 100 ^cm² . In another specific embodiment of the invention, the storage and transport container is prepared such that the Sb-containing liquid has sufficient surface area in contact with the inner wall of the storage and transport container to allow the necessary evaporation of the Sb-containing liquid into a predetermined volume of the headspace. Evaporation occurs so that the headspace of the storage and transport container is replenished with antibacterial vapor as the Sb-containing vapor leaves the headspace and flows along the conduit, thereby generating substantially stable (i.e., stable and continuous) and sufficiently flowing Sb-containing vapor into the arc chamber during the ion implantation procedure. Thermal energy must be added to the Sb-containing liquid to evaporate a given amount of the Sb-containing liquid into vapor. When this energy transfer occurs as a specific portion of the liquid evaporates, the remaining Sb-containing liquid in the storage and transport container can experience a localized temperature drop, falling below the ambient temperature. However, if there is sufficient contact between the inner wall of the storage and transport container and the Sb-containing liquid inside, heat can be transferred by conduction from the container wall, which is exposed to the ambient temperature outside the container, to the Sb-containing liquid. As a result, the Sb-containing liquid can be maintained at an ambient temperature approximately the same as the temperature outside the container. For example, for a liquid volume of approximately 335 mL and a headroom volume of approximately 1.865 L, the surface area of the liquid exposed on the inner wall is at least approximately 110 ^cm² , preferably greater than or equal to approximately 260 ^cm² , and more preferably greater than or equal to approximately 530 ^cm² . As another example, for a liquid volume of approximately 112 mL and a headroom volume of approximately 2.088 L, the surface area of the liquid exposed on the inner wall is at least approximately 50 ^cm² , preferably greater than or equal to approximately 140 ^cm² , and more preferably greater than or equal to approximately 300 ^cm² . For another example, for a liquid volume of about 1 L and a headroom volume of about 1.2 L, the surface area of the liquid exposed on the wall is preferably at least about 300 ^cm² , preferably greater than or equal to about 600 ^cm² , and more preferably greater than or equal to about 1000 ^cm² .

To further increase the surface area of the antimony-containing liquid in contact with the inner wall of the container, various stacked materials may be added to the inside of the storage and transport containers. For example, metals of various shapes can be used, including spheres, bricks, sheets, cylinders, saddles, rings, cubes, screens, and powders. The stacked material may be at least partially immersed in the liquid phase.

In addition to having an appropriate liquid contact surface area with the inner wall of the container, the storage and transport containers are preferably made of a material with sufficient thermal conductivity to facilitate heat conduction to the Sb-containing liquid in the storage and transport containers, so as to maintain a constant temperature during the evaporation of the liquid into the gas phase and the flow of the Sb-containing material. For example, storage and transport containers might be made of carbon steel (54 W/m*K at 293K), stainless steel (12~45 W/m*K at 293K), iron (80 W/m*K at 300K), aluminum (273 W/m*K at 300K), copper (398 W/m*K at 300K), gold (315 W/m*K at 300K), or silver (424 W/m*K at 300K). The thermal conductivity of carbon and stainless steel is obtained from the Engineering Toolbox website, while the elemental thermal conductivity values are taken from Perry's Chemical Engineering Handbook. In a preferred embodiment, the thermal conductivity of the walls of the storage and transport container is greater than or equal to the thermal conductivity of the Sb-containing material. In another preferred embodiment, the thermal conductivity of the walls of the storage and transport container is greater than or equal to 1 W/m*K, more preferably greater than 5 W/m*K, even more preferably greater than or equal to 10 W/m*K, and most preferably greater than or equal to 16 W/m*K.

Other storage conditions for Sb-containing source materials may result in unacceptably low evaporation rates of the liquid source material. For example, if Sb-containing liquid source material is stored in a storage and transport container at pressures equal to or greater than atmospheric pressure, the partial pressure of the gaseous Sb-containing liquid source material may be insufficient because air, _N2 , or any other inert and/or reactive gas species may be inadvertently introduced into the headspace of the storage and transport container during filling operations. Incidentally, in this scenario, contamination of the gaseous Sb-containing material with other pollutants may render the material unsuitable for ion implantation procedures that generally cannot tolerate the introduction of pollutants (including atmospheric pollutants) into the arc chamber.

Alternatively, Sb-containing source materials are stored in storage and transport containers in an impurity-free environment free from trace amounts of moisture and other atmospheric impurities. In the presence of moisture, halogenated Sb-containing compounds can react to form _Sb₂O₃ , _H₂ , HF, or HCl. This trace _- free environment can be achieved in the storage container using several techniques, one of which involves a so-called "freeze-pump-thaw" cycle. In a freeze-pump-thaw cycle, the Sb-containing source material is cooled, causing all Sb-containing vapors to condense from the gas phase and the Sb-containing liquid to freeze, while other contaminants such as moisture and nitrogen remain in the gas phase. After sufficient time has been allowed for the Sb-containing source material to condense, the headspace of the container is emptied using a pump while the container continues to cool to remove virtually all vapor contaminants, and the Sb-containing material remains in the container as a solid, liquid, or mixture thereof. Once the contaminants have been removed, the container is sealed, and the Sb-containing material, in its solid, liquid, or mixture thereof, is heated to ambient temperature to reform into a liquid and vapors in substantial equilibrium with the liquid. In this way, moisture and other impurities (especially atmospheric impurities) are prevented from being introduced into the storage and transport containers. As an alternative or incidental approach, other technologies may be used to achieve a moisture- and gas-free environment for Sb-containing materials, including but not limited to passivating the inner surface of the container with fluorine.

In one specific embodiment, the resulting gaseous composition includes impurities in the headspace, which are no more than 5% by volume. The diverse gaseous impurities include 0 to 4% by volume _N2 , 0 to 0.5% by volume _O2 , 0 to 0.49% by volume HF, and 0 to 0.01% by volume _H2O ; the remainder is the gaseous phase constituting the antimony-containing material. High-purity antimony-containing materials can have a liquid phase containing no more than 1% by volume of liquid phase impurities, wherein the liquid phase impurities include 0 to 0.1% by volume _N2 , 0 to 0.1% by volume _O2 , 0 to 0.6% by volume HF, 0 to 0.1% by volume _SbF3 , and 0 to 0.1% by _{volume Sb2O3} ; the remainder constitutes the liquid phase of the antimony-containing material.

The harmful effects of carbon-based deposits during Sb ion implantation are preferably avoided by this invention. The Sb-containing source material is composed of molecules represented by carbon-free chemical formulas to reduce or eliminate the formation of carbon-based deposits in the arc chamber and throughout other areas of the ion source. Examples of carbon-based deposits include, but are not limited to, C, CF, and CCl compounds. Carbon-based deposits can reduce ion source lifetime by forming fibrous or other diverse shapes of deposits along various components of the ion implanter (including the extraction plate, where carbon-based deposits can distort the shape of the ion beam). Alternatively or incidentally, carbon-based deposits can deposit and accumulate as residual particles on the substrate. The presence of carbon in the plasma can also reduce the Sb beam current because the formed carbon ions become free and available, thus diluting the plasma. Accordingly, the present invention preferably utilizes an Sb-containing source material represented by a carbon-free chemical formula. In this way, avoiding carbon in the Sb-containing source material reduces or eliminates the introduction of carbon-derived deposits into the arc chamber and related harmful effects.

In a preferred embodiment, antimony pentafluoride ( _SbF5 ) is an Sb-containing source material used for ion implantation. _SbF5 is a corrosive liquid, a relatively strong Lewis acid, and reacts violently with moisture to produce _Sb₂O₃ and HF. Thus, the _SbF5 source material is stored in a storage and transport container under sub-atmospheric pressure conditions, in an environment containing less than ₅ % by volume of moisture and other gaseous impurities. In the storage and transport container operatively connected to an arc chamber, _SbF5 can remain liquid at approximately 25°C with a vapor pressure of approximately 10 Torr.

Other source materials are also considered. For example, in another specific embodiment of the invention, _SbCl₅ is an antimony-containing source material suitable for ion implantation. In a storage and transport container operatively connected to an arc chamber, _SbCl₅ remains liquid at approximately 30°C and has a vapor pressure of 1.7 Torr. Other source materials may also be used according to the applicable criteria of the invention, as described herein.

Despite the stability of _SbF5 and the advantages of using liquid-based materials for Sb ion implantation, the inventors have recognized a design challenge with _SbF5 and other fluorinated Sb compounds: the presence of fluorine in the compounds can lead to an excess of fluoride ions in the plasma. Fluoride ions can propagate in what is known as the "halogen cycle," where excess halogen ions can etch the tungsten chamber walls onto the cathode to produce tungsten fluoride species (generally represented by WFx), which can migrate to the hot ion source filaments where tungsten can be deposited. Depositing tungsten tends to increase the operating voltage of the ion source, which in turn increases the amount of W deposited on the ion source filaments until the ion source may eventually degrade. This halogen cycle tends to reduce the lifetime of the ion source.

To mitigate the halogen cycle effect, a hydrogen-containing compound can be introduced during the use of the _SbF5 or other Sb-containing source materials (especially those containing fluorine atoms or other halogens) conceived in this invention. The hydrogen-containing compound can be introduced into the arc chamber in any possible manner, including by sequentially or simultaneously flowing the hydrogen-containing compound with the _SbF5 or other Sb-containing source materials conceived in this invention. Alternatively, the hydrogen-containing compound can be stored as a mixture with the _SbF5 or other Sb-containing source materials conceived in this invention. Suitable hydrogen-containing compounds include, but are not limited to, _{H2 , CH3F} , _CH2F2 , _Si2H6 , _PH3 , _AsH3 , _SiH4 , _GeH4 , _B2H6 , _CH4 , _NH3 , or _{H2S ,} and any combination _thereof .

The amount of hydrogen-containing compound introduced into the arc chamber to mitigate the halogen cycle should be an effective amount, capable of neutralizing or eliminating the harmful effects of fluorine or other halogens that may be present in the Sb-containing source material of the present invention. When using _SbF5 , the effective amount of hydrogen-containing compound is preferably at least about 20% by volume of the overall composition of _SbF5 and the hydrogen-containing compound, to provide an adequate amount of hydrogen atoms to mitigate the harmful effects of the halogen cycle. As used herein and throughout, the term "effective amount" means the amount of a particular material (e.g., a hydrogen-containing compound) required to achieve the stated objective (e.g., neutralizing or eliminating the harmful effects of fluorine or other halogen ions that may arise due to the halogen cycle or other reasons during ion implantation in a specific formulation of an Sb ion species). In one example, the volume percentage of the hydrogen-containing compound required to alleviate the halogen cycle can be approximately 50% of the volume of the constituent mixture of _SbF5 and the hydrogen-containing compound formed in the arc chamber. It should be understood that the effective amount of the hydrogen-containing compound can be greater than approximately 50% of the total composition of _SbF5 and the hydrogen-containing compound.

Using the liquid source material conceived in this invention, which conforms to the applicable criteria defined herein, and avoiding solid Sb-containing sources in this invention, includes several procedural advantages. For example, when using the Sb-containing source material of this invention, overheating is reduced or completely avoided, typically to properly volatilize the solid Sb-containing source and prevent its condensation and deposition along the conduits and flow paths of the ion implantation system. At a minimum, conventional Sb-containing solid sources require heating the conduits extending between the storage and transport containers and the arc chamber to prevent the vaporized but potentially easily condensed Sb-containing solid source from condensing. In contrast, this invention reduces or eliminates in-tube heating. This invention also reduces or eliminates the risk of Sb-containing materials depositing and accumulating on the chamber walls and/or ion source filaments. Avoiding such excessive temperatures also reduces or eliminates the tendency for decomposition and side reactions that can make the Sb ion implantation process difficult to control.

Furthermore, this invention eliminates the need for a carrier gas or reactive gas. In contrast, for example, when a solid Sb source is plated onto a surface adjacent to the arc chamber, the surface must be heated to an elevated temperature to vaporize the solid Sb source, in which case a carrier gas or reactive gas has already been used. The carrier gas or reactive gas then guides the vaporized Sb source into the arc chamber. Because a stable, sufficient, and continuous flow of antimony vapor can be generated, this invention can potentially eliminate the need for a carrier gas. Incidentally, eliminating the carrier gas allows for the delivery of high-purity antimony vapor. Conventional processes that require a carrier gas to allow antimony flow cannot deliver the high purity achieved by this invention.

Referring to Figure 1, an exemplary beam ion implantation device according to the principles of the present invention is shown. The beam ion implantation system is used to perform ion implantation procedures. The components of the beam ion implantation system are shown in Figure 1. The Sb-containing liquid source material 101 is selected to have an appropriate vapor pressure according to the principles of the present invention. The Sb-containing source material 101 is stored in a storage and transport container located in a gas chamber 100, as shown in Figure 1. The Sb-containing liquid source material 101 is stored in an environment with only trace amounts of impurities. The Sb-containing liquid source material 101 is further represented by a carbon-free chemical formula. In a preferred embodiment, the Sb-containing liquid source material 101 is _SbF5 . Alternatively, the Sb-containing liquid source material 101 is _SbCl5 . One or more hydrogen-containing compounds may optionally be included in the gas chamber 100 and flow into the arc chamber 103 in an effective amount to mitigate the halogen cycle effect when using Sb-containing materials including halogens (such as _SbF5 or _SbCl5 ).

The Sb-containing liquid source material 101 is stored as a liquid phase, which is substantially in equilibrium with the corresponding gas phase occupying the headspace of the storage and transport container. The vapor pressure of the Sb-containing source material 101 is sufficient to reduce or eliminate the heating of the pipeline between the gas chamber 100 and the arc chamber 103, thereby enabling process stability control as previously described. The gas phase of the Sb-containing liquid material 101 is configured to flow in a substantially continuous and appropriate flow rate in response to the vacuum pressure conditions downstream of the gas chamber 100. The vapor is present in the headspace of the storage and transport container and flows into the pipeline, and then flows along it toward the arc chamber 103. The vapor pressure of the Sb-containing source material in the storage and transport container in the gas chamber 100 is sufficient to allow the gaseous Sb-containing source material to flow steadily along the conduit into the arc chamber 103. The gaseous Sb-containing liquid material 101 is introduced into the arc chamber 103 to ionize the material 101. Energy is introduced into the arc chamber 103 to ionize the Sb-containing vapor. A flow control device 102 (which may include one or more mass flow controllers and corresponding valves) is used to control the vapor flow rate at a predetermined value. The procedure of FIG1 avoids excessive temperature (typically required by conventional solid Sb-containing sources) and controls the vapor flow at the desired flow rate described herein to allow the ion implanter to have stable and controlled operation. Ionization of Sb-containing materials can generate a variety of antimony ions. An ion beam extraction system 104 is used to extract antimony ions from an arc chamber 103 in the form of an ion beam with the desired energy. Extraction can be performed by applying a high voltage across the extraction electrode. The beam is transported through a quality resolver/filter 105 to select the Sb ion species to be implanted. The ion beam can then be accelerated/decelerated 106 and transported to the surface of a target workpiece 108 (i.e., a substrate) positioned at an end station 107 to implant the Sb ions into the workpiece 108. The workpiece may, for example, be a semiconductor wafer or a similar target object requiring ion implantation. The Sb ions in the beam collide with and penetrate the surface of the workpiece to a specific depth to form a doped region with the desired electrical and physical properties.

It should be understood that the novel Sb-containing material of this invention can be used in other ion implantation systems. For example, Sb ions can also be implanted using a plasma immersion ion implant (PIII) system as shown in Figure 2. This system includes a gas chamber 200, the structure of which is similar to that of the wire ion implantation device 100. The operation of the PIII system is similar to that of the wire ion implantation system of Figure 1. Referring to Figure 2, the gaseous Sb-containing liquid source material of this invention is introduced from the Sb-containing liquid source material 201 into the plasma chamber 203 by a flow control device 202. Sb-containing liquid source material 201 represents a storage and transport container constructed to store an Sb-containing liquid phase in substantial equilibrium with a corresponding gas phase occupying the headspace of the storage and transport container. Sb-containing liquid source material 201 is stored in an environment with only trace amounts of impurities. Sb-containing liquid source material 201 is further represented by a carbon-free chemical formula. In a preferred embodiment, Sb-containing liquid source material 201 is _SbF₅ . Alternatively, Sb-containing liquid source material 201 is _SbCl₅ .

The vapor pressure of the Sb-containing liquid source material 201 is sufficient to reduce or eliminate the heating of the pipeline between the gas chamber 200 and the plasma chamber 203, thereby enabling process stability control as described above. The gaseous Sb-containing liquid source material 201 is configured to flow in the gas phase at a substantially continuous and appropriate flow rate in response to the vacuum pressure conditions downstream of the gas chamber 200. The gas phase is present in the head space of the storage and transport container and flows into the pipeline, and then flows along the pipeline toward the plasma chamber 203. The vapor pressure of the Sb-containing source material in the storage and transport container in the gas chamber 200 is sufficient to allow the gaseous Sb-containing source material to flow stably along the pipeline into the plasma chamber 203. As the gaseous Sb-containing liquid material is introduced into the plasma chamber 203, energy is subsequently provided to ionize the Sb-containing vapor and generate Sb ions. The Sb ions present in the plasma are accelerated toward the target workpiece 204. It should be understood that one or more hydrogen-containing compounds may be selectively included in an effective amount in the gas chamber 200 and flow into the plasma chamber 203 to mitigate the halogen cycle effect when using Sb-containing materials including halogens (such as _SbF5 or _SbCl5 ).

In another embodiment of the invention, a storage and transport container for the Sb-containing source material disclosed herein is provided, as shown in Figure 3. The storage and transport container allows for the safe packaging and transport of the Sb-containing source material of the invention. The Sb-containing source material of the invention is contained within a container 300. The container 300 is equipped with an inlet port 310 to allow the container 300 to be filled with the desired Sb-containing source material. This port can also be used to purge the interior of the container 300 with an inert gas and empty the container 300 before filling with the desired Sb-doped material. In one example, the container 300 can be used for a freeze-pump-thaw cycle to create an environment with less than 5% impurities in the headspace based on the total headspace volume. Storage and transport container 300 (Example I) includes a headspace 335 of predetermined volume, and storage and transport container 300 (Example II) includes a headspace 336 of predetermined volume, wherein containers 300 (Examples I and II) are constructed and manufactured in accordance with the principles of the present invention.

An outlet port 320 is provided to extract gaseous Sb-containing material from the headspace of container 300. A vacuum-actuated check valve 330 is located upstream of the outlet port and responds to sub-atmospheric pressure conditions downstream of container 300 to deliver Sb-containing material at a controlled flow rate. This vacuum-actuated check valve 330 enhances safety when handling the diverse Sb-containing materials of the invention. When valve 321 is open to atmospheric pressure, the vacuum-actuated check valve 330 prevents the introduction of any air or other contaminants into container 300, thus mitigating the risks of contamination of the gaseous Sb-containing material occupying the headspace of container 300 and reduced partial pressure. In this way, high-purity Sb-containing materials can be safely maintained during storage, transportation, and use, thereby maintaining an appropriate vapor pressure for the extracted Sb-containing source material to generate the required flow rate during ion implantation. The vacuum-actuated check valve 330 can be located outside the container 300 (Example I). Alternatively, the vacuum-actuated check valve 330 can be located inside the container 300 (Example II). The container 300 is fluidly connected to an exhaust flow path, wherein the vacuum-actuated check valve 330 is actuated to allow controlled flow of Sb-containing source material from the internal volume of the container 300 in response to sub-atmospheric pressure conditions achieved along the exhaust flow path.

The storage and transport container 300 may be a cylinder that stores the Sb-containing material as at least a portion of the vapor phase under sub-atmospheric pressure conditions. The Sb-containing material is stored therein under sub-atmospheric pressure conditions. The Sb-containing material remains chemically stable and does not undergo decomposition within the cylinder 300. Preferably, the Sb-containing material is stored as a liquid at the ambient temperature (10–35°C). In one embodiment, the vapor pressure is greater than about 1 Torr. In another embodiment, the vapor pressure is greater than about 3 Torr, more preferably greater than about 5 Torr.

The cylinder 300 preferably includes a dual-port valve assembly mechanically connected to it. The dual-port valve, shown in FIG. 4, includes a filling port valve and a discharge port valve, wherein the filling port valve is fluid-connected to the interior of the cylinder to introduce Sb-doped material therein. The discharge port valve is fluid-connected to a flow discharge path extending from the interior of the cylinder to the exterior to discharge the antimony-doped material. A check valve 330 is positioned along the flow discharge path, thereby being configured to move from a closed position to an open position in response to sub-atmospheric pressure conditions outside the cylinder. The head space 401 has a predetermined volume according to the principles of the invention.

Other storage containers are also considered. For example, in alternative selective embodiments, the antimony-doped material may be stored and distributed from an adsorbent-based transport system. A variety of suitable adsorbents are considered, including, but not limited to, carbon-based adsorbents or metal-organic frameworks.

Several modifications to the cylinders of Figures 3 and 4 are considered without departing from the scope of the invention. For example, it should be understood that the dual-port valves of Figures 3 and 4 can be used without the use of check valves. Furthermore, it should be understood that the principles of the invention can be used for storage and transport containers with single-port filling and dispensing without the use of check valves.

In another specific embodiment, the present invention may employ the ^UpTime® delivery device, commercially available from Praxair (Danbury, Connecticut) and as disclosed in U.S. Patent Nos. 5,937,895, 6,045,115, 6,007,609, 7,708,028, 7,905,247 and U.S. Patent Publication No. 2016/0258537 (all of which are incorporated herein by reference in their entirety), to safely deliver a controlled flow rate of Sb-containing gaseous material from container 300 to an ion device for Sb ion implantation. The vacuum-actuated check valve in the ^UpTime® conveyor is used to prevent contamination from atmospheric air and other gases that may be present in the surrounding environment and penetrate into the container, contaminating Sb-containing precursor materials and reducing their partial pressure.

Other suitable sub-atmospheric pressure conveying devices may include pressure regulators, check valves, flow restrictors, and flow orifices arranged in various configurations. For example, two pressure regulators may be configured in series within the container to reduce the container pressure of the gaseous Sb-containing source material to a predetermined pressure acceptable to a downstream mass flow controller along the fluid discharge line.

The container or cylinder 300, along with its contemplated variations, may be configured in combination with a wire-connected ion implantation system (Figure 1), whereby the container or cylinder 300 is operatively connected to the system via a network of flow lines or conduits extending therefrom. Advantageously, the conduits are further characterized by eliminating or reducing in-tube heating compared to conventional Sb-containing sources.

Alternatively, the container or cylinder 300, along with its variations, may be configured to be integrated with a plasma immersion system (Figure 2), whereby the container or cylinder 300 is operatively connected to the plasma immersion system via a network of flow lines or conduits extending therefrom. Advantageously, the conduits are further characterized by eliminating or reducing the amount of heat generated in the conduits compared to conventional Sb-containing sources.

This invention offers numerous advantages. For example, using the liquid-based Sb-containing precursor of this invention to deliver the Sb-containing gas phase for Sb ion implantation, followed by switching to different gaseous dopant sources, generally requires less time compared to using a solid-based Sb-containing precursor for Sb ion implantation followed by different gaseous dopant sources. Specifically, using the liquid-based Sb-containing precursor of this invention to deliver the Sb-containing gas phase, compared to a solid Sb source, reduces the start-up time required to switch to different dopant species for ion implantation, thereby resulting in maximum wafer yield for the implantation machine. For example, an implanter using solid arsenic (As) or solid phosphorus (P) as source material to implant specific ion species can be expected to take approximately 30 minutes to tune the ion beam, while using gaseous _AsH3 or gaseous _PH3 source material can generally be expected to take only about 4 minutes. The term "tuning" or "tuning" as used here and throughout refers to a procedure that produces a beam of target ion species with only a specific beam current and size. In contrast, with solid Sb-containing source materials, the mass flow in the arc chamber is controlled by the vaporizer temperature required for sublimation, where the Sb-containing source is stored to ensure that the solid source is sufficiently heated into the gas phase before being delivered to the arc chamber. When considering the time required to heat the solid Sb-containing source material into its gaseous phase, regulate the beam, and then cool the solid Sb-containing source during the ion implantation procedure, the total time can be approximately 30–90 minutes to switch to another dopant species; while transporting the gaseous dopant source derived from the Sb-containing liquid precursor can take approximately 5–10 minutes. The net result can be a significant increase in yield.

Incidentally, the liquid-based Sb-containing precursor of this invention can be placed in the same gas chamber as other doped sources (e.g., as shown in Figures 1 and 2) without additional heating. In contrast, Sb-containing solid sources require a separate vaporizer positioned along a conduit extending to the arc chamber to ensure that the Sb-containing vapor does not condense again. This requires more space than is possible and further increases the complexity and cost of the ion implantation procedure.

<Experimental Description>

A flow test system was constructed to test the flowability of antimony pentafluoride (SbF5 ₎ , which is liquid at room temperature and has a vapor pressure of 10 Torr at 25°C. For each experiment, the flow system consisted of: a manifold with a pressure sensor connected to it to read the pressure exerted by the _SbF5 vapor in the headspace; a mass flow controller within the manifold to measure and control the vapor flow; and a roughing vacuum pump to maintain a vacuum pressure downstream of the mass flow controller at less than 1 x ^10⁻² Torr. The cylinders used in each experiment were made of carbon steel and equipped with a two-port valve consisting of a filling port and a usage port. The cylinder was connected to the manifold.

Generally, the cartridge systems filled with liquid _SbF5 for flow testing are prepared as follows. Each cartridge is filled with liquid _SbF5 under an atmosphere of _N2 to ensure that the liquid _SbF5 does not react with atmospheric water vapor. The purity of the liquid _SbF5 is 99% by volume. To remove _N2 , water vapor, and any other gaseous impurities from the headspace of the cartridge to a trace amount, a two-stage freeze-pump-thaw cycle is performed on each cartridge as described previously. In one freeze-pump-thaw cycle, the cartridge is placed in an ice bath for more than 20 minutes to allow the _SbF5 vapor to condense from the gas phase into liquid and to freeze the _SbF5 liquid, while _N2 , water vapor, and any other gaseous impurities remain in the gas phase in the headspace of the cartridge. The cylinder was then opened and evacuated with a vacuum pump for more than one minute to remove trace amounts of _N2 , water vapor, and any other gaseous impurities from the headspace. The cylinder was then closed and isolated from the pump. After isolation, the ice bath was removed to allow the cylinder to warm to ambient temperature, thereby allowing the re-formation of liquid _SbF5 and the corresponding _SbF5 vapor.

Before starting each experiment, open the cylinder valve to allow _SbF5 vapor to exit the headspace through the usage port and enter and fill the manifold section to the mass flow controller. With _SbF5 vapor filling the manifold, the pressure sensor can read the pressure therein, which represents the vapor pressure of _SbF5 in the cylinder.

Next, flow tests were conducted to determine whether it was possible to achieve a stable, continuous, and adequate flow of _SbF5 vapor from the cylinder. The key details and corresponding results of each test are described below.

<Comparative Example 1>

A 420 mL carbon steel canister was filled with 300 g (100 mL) of liquid _SbF5 . The headspace volume within the canister was 320 mL. The canister and flow manifold were maintained at an ambient temperature of 25°C, resulting in an _SbF5 vapor pressure of 10 Torr as read by a pressure sensor. No external heating was used. No carrier gas was used. The continuous flow characteristics of the canister were tested. The canister could not maintain a continuous flow of _SbF5 greater than 0.3 sccm.

<Comparative example 2>

A 2.2L carbon steel canister was filled with 1 kg (335 mL) of liquid _SbF5 . The headspace volume of the canister was 1.865 L. The canister and valve were heated to 40°C to increase the vapor pressure, resulting in an _SbF5 vapor pressure of 15 Torr as read by the pressure sensor. No carrier gas was used. The manifold and mass flow controller were not heated and maintained at an ambient temperature of 22°C. The continuous flow characteristics of the canister were tested. The canister could not maintain a continuous flow of _SbF5 greater than 0.3 sccm because _SbF5 vapor condensation caused obstruction in the flow path.

<Implementation Example 1>

A 2.2L carbon steel canister was filled with 1 kg (335 mL) of liquid _SbF5 . The headspace volume of the canister was 1.865 L. The canister and flow manifold were maintained at an ambient temperature of 25°C, resulting in an _SbF5 vapor pressure of 10 Torr as read by a pressure sensor. No external heating was used. No carrier gas was used. The continuous flow characteristics of the canister were tested. The canister was able to maintain a continuous flow of _SbF5 at 2 sccm.

<Implementation Example 2>

A 2.2L carbon steel canister was filled with 1 kg (335 mL) of liquid _SbF5 . The headspace volume of the canister was 1.865 L. The canister and flow manifold were maintained at an ambient temperature of 22°C, resulting in an _SbF5 vapor pressure of 7 Torr as read by a pressure sensor. No external heating was used. No carrier gas was used. The continuous flow characteristics of the canister were tested. The canister was able to maintain a continuous flow of _SbF5 at 2 sccm.

<Implementation Example 3>

A 2.2L carbon steel canister was filled with 335g (112mL) of liquid _SbF5 . The headspace volume of the canister was 2.088L. The canister and flow manifold were maintained at an ambient temperature of 22°C, resulting in an _SbF5 vapor pressure of 7 Torr as read by a pressure sensor. No external heating was used. No carrier gas was used. The continuous flow characteristics of the canister were tested. The canister was able to maintain a continuous flow of _SbF5 at 2 sccm.

<Implementation Example 4>

A 2.2L carbon steel canister was filled with 335g (112mL) of liquid _SbF5 . The headspace volume of the canister was 2.088L. The canister and flow manifold were maintained at an ambient temperature of 25°C, resulting in an _SbF5 vapor pressure of 10 Torr as read by a pressure sensor. No external heating was used. No carrier gas was used. The continuous flow characteristics of the canister were tested. The canister was able to maintain a continuous flow of _SbF5 at 2 sccm.

<Implementation Example 5>

A 2.2L carbon steel canister was filled with 1 kg (335 mL) of liquid _SbF5 . The headspace volume of the canister was 2.088 L. The canister and flow manifold were maintained at an ambient temperature of 18°C, resulting in an SbF5 vapor pressure of ₅ Torr as read by a pressure sensor. No external heating was used. No carrier gas was used. The continuous flow characteristics of the canister were tested. The canister was able to maintain a continuous flow of _SbF5 at 2.5 sccm.

As can be seen, this invention provides a feasible solution, in one respect, for Sb-containing sources used in ion implantation, including Sb-containing solid-state sources that are difficult to deliver consistently into the arc chamber due to low vapor pressure and limited thermal stability.

It should be understood that the principles of this invention can be applied to other procedures besides ion implantation that require sufficient, continuous, and stable flow of gaseous antimony-containing materials.

While specific embodiments considered to be part of the invention have been shown and described, it will be understood that a variety of modifications and changes in form and detail can be easily made without departing from the spirit and scope of the invention. Therefore, the invention is not intended to be limited to the precise forms and details shown and described herein, nor to any part smaller than the overall invention disclosed herein and claimed below.

100: Gas Box

101: Materials containing Sb source material

102: Flow control device

103: Ion Source Chamber

104: Ion Beam Extraction

105: Quality Analyzer/Filter

106: Acceleration/Deceleration

107: Embedded in the client application

108: Target workpiece

Claims (11)

A subatmospheric pressure storage and transport container configured to transport high-purity vapor-phase antimony-containing materials, comprising: a storage and transport vessel configured to store the antimony-containing material in a liquid phase under subatmospheric pressure conditions, wherein the liquid phase is substantially in equilibrium with the high-purity vapor-phase antimony-containing material, and the high-purity vapor-phase antimony-containing material is subjected to a vapor pressure less than atmospheric pressure, wherein the high-purity vapor phase has a total volume of approximately 95% or more. The storage and transport container comprises multiple walls having sufficient surface area to contact the liquid phase, and further wherein the multiple walls exhibit thermal conductivity to enhance thermal conduction to the liquid phase; the storage and transport container is characterized in that: during the delivery of the high-purity gaseous antimony-containing material, there is no external heating and no carrier gas; wherein the liquid phase contains a total liquid phase impurity amount ranging from 0 to 1 volume % impurities, and further wherein the liquid phase impurities contain 0 to 0.1 volume % N. _2. 0 to 0.1% by volume of _O2 , 0 to 0.6% by volume of HF, 0 to 0.1% by volume of _SbF3 , 0 to 0.1% by volume _{of Sb2O3} , and the remainder being the antimony-containing material in the liquid phase. As in claim 1, a storage and transport container operating at sub-atmospheric pressure, wherein the antimony-containing material is represented by a carbon-free chemical formula to reduce or eliminate the formation of carbonaceous deposits in the arc chamber of the ion implanter and throughout other areas of the ion source. As in claim 2, a storage and transport container operating at sub-atmospheric pressure, wherein the thermal conductivity of the plurality of walls ranges from 1 to 425 W/m-K, and the antimony-containing material is represented by a carbon-free chemical formula to reduce or eliminate the formation of carbonaceous deposits in the arc chamber and throughout other areas of the ion source. A subatmospheric pressure storage and transport container configured to transport high-purity vapor-phase antimony-containing materials, the container comprising: a storage and transport vessel configured to store the antimony-containing material in a liquid phase under subatmospheric pressure conditions, wherein the liquid phase is substantially in equilibrium with the high-purity vapor-phase antimony-containing material occupying a predetermined volume of the headspace within the storage and transport vessel, and the high-purity vapor-phase antimony-containing material is subjected to a vapor pressure less than atmospheric pressure. The predetermined volume of the head space is approximately 95% by volume or greater; the dimensions of the predetermined volume of the head space are adjusted to receive a sufficient amount of the high-purity vapor-phase antimony-containing material; the storage and transport container is characterized in that: during the delivery of the high-purity vapor-phase antimony-containing material, there is no external heating and no carrier gas; wherein the liquid phase contains a total amount of liquid phase impurities ranging from 0 to 1% by volume, and further wherein the liquid phase impurities contain 0 to 0.1% by volume N. _2. 0 to 0.1% by volume of _O2 , 0 to 0.6% by volume of HF, 0 to 0.1% by volume of _SbF3 , 0 to 0.1% by volume _{of Sb2O3} , and the remainder being the antimony-containing material in the liquid phase. As in claim 4, a storage and transport container at subatmospheric pressure, wherein the surface area of the liquid phase exposed to the high-purity gas phase is at least about 50 ^cm² , and further wherein the predetermined volume of the headspace is 1 L or greater. The storage and transport containers for pressures below atmospheric pressure, as described in claim 4, further include an adsorbent. Such as the storage and transport container below atmospheric pressure in claim 4, wherein the pressure in the headspace is greater than or equal to 1 Torr. A high-purity antimony-containing material for storage containers comprises a liquid phase and a gas phase. The gas phase contains a total amount of gaseous impurities ranging from 0 to 5 volume %, wherein the gaseous impurities include 0 to 4 volume % _N₂ , 0 to 0.5 volume % _O₂ , 0 to 0.49 volume % HF, 0 to 0.01 volume % _H₂O , and the remainder being the antimony-containing material in the gas phase. The liquid phase contains a total amount of liquid impurities ranging from 0 to 1 volume %, wherein the liquid phase impurities include 0 to 0.1 volume % _N₂ , 0 to 0.1 volume % _O₂ , 0 to 0.6 volume % HF, and 0 to 0.1 volume % SbF₃ _. The antimony-containing material comprises 0 to 0.1% by volume of _Sb₂O₃ and the remainder in the liquid _phase . A method for preparing a storage and transport container at sub-atmospheric pressure, the container being configured to transport a stable, continuous, and sufficiently flowing high-purity vapor-phase antimony source material, the method comprising the following steps: providing a container having multiple walls having a thermal conductivity of 5 W/m*K; passivating the multiple walls with fluorine; then introducing a liquid antimony-containing material into the container in the presence of an inert gas; generating a predetermined headspace volume greater than or equal to about 1 L, the predetermined headspace volume containing trace impurities; and evaporating a sufficient amount of the antimony-containing material into the vapor phase within the predetermined headspace volume, wherein the evaporation step is performed without... The process is carried out by external heating; freezing the antimony-containing material in the liquid phase to form frozen antimony-containing material; condensing the antimony-containing material in the gaseous phase from the predetermined headspace volume to form a condensed high-purity gaseous phase; venting nitrogen, water vapor, the inert gas, and any other gaseous impurities from the predetermined headspace volume; allowing the temperature of the condensed gaseous phase to increase in order to form the high-purity gaseous phase in the predetermined headspace volume; and allowing the temperature of the frozen antimony-containing material to increase in order to reform the liquid phase, wherein the liquid phase contains a total liquid phase impurity amount ranging from 0 to 1 volume % impurities, wherein the liquid phase impurities contain 0 to 0.1 volume % N. _2. 0 to 0.1% by volume of _O2 , 0 to 0.6% by volume of HF, 0 to 0.1% by volume of _SbF3 , 0 to 0.1% by volume _{of Sb2O3} , and the remainder being the antimony-containing material in the liquid phase. The method of claim 9 further comprises performing the following steps: (i) condensation, (ii) venting, and (iii) allowing the condensed high-purity gas phase and the frozen antimony-containing material to warm up in order to re-form the liquid phase and the high-purity gas phase in the predetermined headspace volume; wherein each of steps (i), (ii), and (iii) is performed two or more times to achieve a gaseous impurity in the headspace comprising 0 to 4 volume% _N2 , 0 to 0.5 volume% _O2 , 0 to 0.49 volume% HF, and 0 to 0.01 volume% _H2O , wherein the total amount of the gaseous impurity is 5 volume% or less. A method of using a storage and delivery container, as claimed in claim 1 or 4, at sub-atmospheric pressure and filled with a high-purity antimony-containing material, comprising: operably connecting the container to a downstream ion implantation tool; establishing a pressure downstream of the sub-atmospheric pressure storage and delivery container at a pressure less than the vapor pressure of the high-purity vapor-phase antimony-containing material occupying a predetermined headspace volume of the container; actuating a valve to an open position; and dispensing the high-purity antimony-containing material from the predetermined headspace volume of the container without heating. An antimony-containing material, delivered in a high-purity gaseous phase at a flow rate of 0.1 sccm or greater without a carrier gas; and the high-purity gaseous antimony-containing material flowing toward the ion implantation tool at a flow rate of 0.1 sccm or greater without the carrier gas; and the evaporation of additional antimony-containing material from the corresponding liquid phase in the container without heating, while the high-purity gaseous antimony-containing material continues to be supplied from the head space at a flow rate of 0.1 sccm or greater.